1. Field of the Invention
The present invention relates to a CO2 recovery apparatus and a CO2 recovery method. More specifically, the present invention relates to a CO2 recovery apparatus and a CO2 recovery method configured to reduce the concentration of basic amine compounds, which remain in decarbonated exhaust gas from which CO2 has been removed by gas-liquid contact with an absorbing solution and which is released.
2. Description of the Related Art
The greenhouse effect that occurs due to the release of CO2 into the air has been considered as one of the causes of global warming. The need to address global warming has become urgent. The source of generating CO2 ranges in all fields of human activities that utilize burning of fossil fuels. The demand for suppressing exhaust of gas containing CO2 has become more and more intense. Under such circumstances, CO2 recovery technologies for the thermal power plants which use a lot of fossil fuels, such as the method a amine-based absorbents contact with the flue gas and remove CO2 from the gas, are investigated
In recovering CO2 from exhaust gas by using the amine-based absorbing solution described above, an amine compound may be entrained in the treated gas from which CO2 has been recovered. In order to prevent air pollution that may occur due to the amine compound entrained in the exhaust gas, it is necessary to reduce the amount of amine compounds to be released together with the decarbonated exhaust gas.
JP H10-33938 A discloses a method for collecting an amine compound. More specifically, in the method discussed in JP H10-33938 A, the distributed sulfuric acid is distributed in order to react with entrained amines in the treated gas and make the basic amine sulfate. Subsequently, the treated gas containing the basic amine sulfate is passed through a demister. In this manner, the conventional method collects a basic amine sulfate from the treated gas.
For a CO2 absorption apparatus having the configuration described above, it is desired to reduce the concentration of a basic amine compound that derives from the CO2 absorbing solution entrained in the exhaust gas to a level that is as low as possible. In particular, CO2 recovery plants for the thermal power plant will treated a lot of the flue gas and the entrained amine amount with the flue gas will tend to increase. Further reduction of the entraine amine amount is required.
JP 2011-115724 A discloses a method for further reducing the concentration of components of an absorbing solution. More specifically, JP 2011-115724 A discloses a CO2 recovery apparatus which includes an absorption tower including a CO2 absorption unit configured to absorb CO2 contained in exhaust gas into a basic amine compound absorbing solution by causing the exhaust gas to come into contact with the basic amine compound absorbing solution and at least one washing unit configured to remove basic amine compounds entrained in the decarbonated exhaust gas by causing the decarbonated exhaust gas from which CO2 has been removed by the CO2 absorption unit to come into contact with washing water. The conventional CO2 recovery apparatus further includes an acid washing unit, which is provided downstream in the direction of the flow of the decarbonated exhaust gas in the washing unit and which is configured to further remove basic amine compounds entrained in the decarbonated exhaust gas by causing the decarbonated exhaust gas to come into contact with circulating acid water. The CO2 recovery apparatus is capable of further reducing the concentration of the components of the absorbing solution, which remain in decarbonated exhaust gas and which is to be released together with the decarbonated exhaust gas.